Power plug device is used to connect to a power socket for delivering current to the electrical appliances, such as television, refrigerator, shaver, or hair dryer, and thus the electrical appliances can be operated. Some of the electrical appliances may be used in the moist atmosphere such as bathroom, and hence it is very important that the power plug devices can be used safely in the moist atmosphere and have function of waterproof.
International Protection Marking, Ingress Protection Rating or IP Code is generally known as to define the degree of protection for preventing solid and liquid particles from penetrating into the mechanical or electrical appliances. The first digit of IP Code represents the level of protection against the penetration of external solid particles, and classified by level 0 to 6. The level 0 indicates a null protection against contact and ingress of objects, and the level 6 indicates a complete protection against contact and no ingress of dusts. The higher first digit of IP Code indicates the greater protection against the ingress of objects. The second digit of IP Code represents the level of protection for the enclosure of mechanical or electrical appliances against the ingress of water, and classified by level 0 to 8. The level 0 indicates no protection against the ingress of water, and the level 8 indicates protection for the enclosure of mechanical or electrical appliances immersing water over. The higher numeral indicates the greater protections harmful ingress of water. If the mechanical casings or the electrical enclosures cannot provide any protective level of solid particle protection or liquid ingress protection, the digit will be replaced with the letter X. For instance, a power plug device with protection class IPX7 is known that it has no protection provided against solid particle, but contains protection against temporary submersion when the device is immersed 1000 mm below the surface of the water.
Conventionally, a power plug device with protection class IPX7 is sealed by filling the inner space of the power plug device with an insulating compound completely for increasing the protection against the liquid ingress, such as filling the epoxy. The filled insulating compound often covers the inner elements of the power plug device, including a printed circuit board and a cable.
Except the inner space of the power plug device filled with the insulating compound, the power plug device is normally sealed by using an ultrasonic welding technology. The principle of the ultrasonic welding technology is based on converting the high-frequency of sound signal into the frictional heat by an energy converter. The horn of the energy converter contacts to the plastic material so that the temperature of the contact area increases under the frictional heat generated from the vibration of molecular of the plastic material. When the temperature of the contact area is increased over the melting point of the plastic material, the plastic material will be melt together and form a solid body after cooling down.
The power plug device is employed by filling the insulating compound and by an ultrasonic welding technology for preventing the liquid ingress. However, the weight of power plug device is increasing due to the requirement of more filled insulating compound in the conventional power plug. Thus, the present invention is proposed to overcome the disadvantages mentioned above.